Clearance from combustible materials

75 mm

Appliances that generate heat, such as solid fuel burners, must maintain a minimum separation distance of 75mm from any combustible materials to prevent fire

Appliances that generate heat, such as solid fuel burners, must maintain a minimum separation distance of 75mm from any combustible materials to prevent fire. This clearance applies to various parts of the appliance and its flue system.

Basis in regulation

Part J
Approved Document J
Read the source

How to check it on site

Measure the clearance between heat-producing appliances, flues, and all surrounding combustible materials to ensure it meets the minimum 75mm requirement.

Common failure

Reduced or absent clearances between heat sources and combustibles pose a severe fire hazard.

Last updated 23 August 2026. This is our editorial summary of publicly available regulation, not building control approval or a warranty determination.

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Minimum

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Minimum

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exact

32mm waste pipe support

32 mm

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Minimum

Headroom over a stair

2000 mm, reducing to 1900 mm at the centre of a loft conversion stair and 1800 mm at the side

Stairs and landings within a dwelling

Maximum

Smoke alarm siting distances

Within 7.5 m of the door to every habitable room, within 3 m of every bedroom door, and at least 300 mm from any wall or light fitting

Ceiling-mounted mains-powered alarms on circulation routes

Range

Gradient of a branch discharge pipe

18 to 90 mm per metre for a 75 mm or 100 mm branch

Measured along the branch from the appliance to the stack